The invention relates to an improved process for the production of 13-oxabicyclo[10.3.0]pentadecane, a valuable ambergris fragrance with a very high fixative capacity. The following manufacturing method has been proposed in DOS No. 2,810,107:
1. Reformatskii reaction of cyclododecanone (I) with bromoacetic acid ester to obtain the corresponding hydroxy ester II.
2. Reaction of II with a strong acid to form the lactone III.
3. Reduction of III to the diol IV.
4. Cyclization with splitting of water in the presence of p-toluenesulfonic acid to obtain 13-oxabicyclo[10.3.0]pentadecane. ##STR1##
The bromoacetic acid ester utilized in this process is highly toxic and is an irritant to mucous membranes. Its use, therefore, required special safety measures. Additionally, the Reformatskii synthesis can be performed only by highly skilled personnel and is difficult to accomplish under industrial conditions.
The production of 13-oxabicyclo[10.3.0]pentadecane according to the process of DOS No. 3,040,994 proceeds via the following steps:
1. Bromination of cyclododecanone in the .alpha.-position with respect to the carbonyl group to obtain the bromoketone VI.
2. Reaction of .alpha.-bromocyclododecanone VI with the dialkyl ester of sodium malonic acid to obtain the dialkyl ester of 2-(2-oxocyclododec-1-yl)malonic acid VII.
3. Saponification with decarboxylation of VII to give the ketocarboxylic acid VIII.
4. Esterification of VIII with a low-boiling alcohol to obtain the corresponding ester IX.
5. Reduction of the keto ester IX with a metal hydride, such as NaBH.sub.4, yields 2-(2-hydroxyethyl)cyclododecanol IV.
6. Cyclization of IV gives rise to V, as in the process of DOS No. 2,810,107. ##STR2##
Even this improved manufacturing method still exhibits several drawbacks:
Bromine and sodium malonic acid dialkyl esters are expensive chemicals, and their use requires special industrial safety measures, such as, for example, complete exclusion of moisture during the reaction of the sodium compound. Moreover, only especially highly skilled personnel are permitted to handle highly toxic bromine and conduct the reaction of VI to VII which, according to DOS No. 3,040,994, requires "strictly controlled reaction conditions".